Method for producing an object from a precursor, and use of a radically crosslinkable resin in an additive production method

ABSTRACT

The invention further relates to the use of a free-radically crosslinkable resin having a viscosity (23° C., DIN EN ISO 2884-1) of ≥5 mPas to ≤100000 mPas in an additive manufacturing process, wherein the resin comprises a curable compound having isocyanurate groups, NCO groups and olefinic C═C double bonds. The invention finally relates to a polymer obtainable by crosslinking such a resin.

The present invention relates to a process for producing an object froma precursor, comprising the steps of:

-   I) depositing a free-radically crosslinked resin atop a carrier to    obtain a ply of a construction material joined to the carrier which    corresponds to a first selected cross section of the precursor;-   II) depositing a free-radically crosslinked resin atop a previously    applied ply of the construction material to obtain a further ply of    the construction material which corresponds to a further selected    cross section of the precursor and which is joined to the previously    applied ply;-   III) repeating step II) until the precursor is formed;    wherein the depositing of a free-radically crosslinked resin at    least in step II) is effected by exposure and/or irradiation of a    selected region of a free-radically crosslinkable resin    corresponding to the respectively selected cross section of the    precursor, and wherein the free-radically crosslinkable resin has a    viscosity (23° C., DIN EN ISO 2884-1) of ≥5 mPas to ≤100000 mPas.

The invention further relates to the use of a free-radicallycrosslinkable resin having a viscosity (at 23° C. measured with aWells/Brookfield cone-plate viscometer according to DIN EN ISO 2884-1)of ≥5 mPas to ≤100000 mPas in an additive manufacturing process, whereinthe resin comprises a curable compound having isocyanurate groups, NCOgroups and olefinic C═C double bonds. The invention finally relates to apolymer obtainable by crosslinking such a resin.

Polymers having a polyisocyanurate structure are known for their highthermal stability and flame resistance. Polyisocyanurate-containingfoams (PUR/PIR-foams) based on aromatic 4,4′-diphenylmethanediisocyanate (MDI) and polyether polyols and polyepoxides are widelyused on account of their very low thermal conductivity for example, inparticular as high-performance insulating materials.

Polyisocyanurates also find practical application as crosslinking agentsin paint chemistry, the production of which involves stopping thetrimerization reaction at low conversions and removing excess unreactedmonomeric diisocyanate. Thus, in the production of crosslinking agentsbased on isocyanurates proceeding from aliphatic and mixed aliphatic andaromatic monomeric diisocyanates, DE 31 00 263; GB 952 931, GB 966 338;U.S. Pat. Nos. 3,211,703 or 3,330,828 envisage performing the reactioneither in dilute conditions or only up to low conversion values withvery precise temperature control. Crosslinked polyisocyanurate plasticsmaterials are specifically not formed, only oligomeric, low-viscosity,soluble products. U.S. Pat. No. 6,133,397 discloses a coatingcomposition having a low content of volatile organic compounds and aviscosity (ZAHN-cup 2) of less than about 200 seconds. The compositionconsists essentially of at least one aliphatic polyisocyanate, a solventin an amount between 0% and 45% based on the weight of thepolyisocyanate in the composition, and a trimerization catalyst. Thecomposition is essentially free from volatile mono- and diisocyanates.

Isocyanurates constructed based on isocyanates having an NCOfunctionality of more than two retain free NCO groups which may befurther functionalized by subsequent reactions.

EP 0 000 658 A1 discloses a process for producing an ethylenicallyunsaturated isocyanurate in which a polyisocyanate is reacted with ahydroxyl component containing a monohydric alcohol, wherein saidisocyanurate contains a vinylidene group but no allyl group, wherein thereaction is performed in the presence of a copper salt to obtain anisocyanate-containing urethane, wherein the amounts of the hydroxylcomponent and the polyisocyanate are chosen such that after saidreaction 0.75 to 1.6 mol of unconverted isocyanate groups per mole ofpolyisocyanate used are retained. Subsequently, a catalytic amount of anisocyanate trimerization catalyst which initiates trimerization of theisocyanate-containing urethane without causing gelation is added so thatthe isocyanate-containing urethane is timerized to produce anethylenically unsaturated isocyanurate. In one embodiment the monohydricalcohol may be hydroxypropyl methacrylate, hydroxypropyl acrylate,hydroxyethyl methacrylate, hydroxyethyl acrylate, pentaerythritoltriacrylate, pentaerythritol trimethacrylate, or a mixture thereof.

EP 0 315 020 A2 relates to a process for producing compounds comprisingisocyanurate groups and olefinic double bonds by reaction of a) apolyisocyanate component comprising isocyanurate groups and containingpolyisocyanates with b) an olefinically unsaturated alcohol componentconsisting of at least one hydroxyalkyl ester of acrylic acid ormethacrylic acid, characterized in that one uses a) as thepolyisocyanate component (i) N,N′,N″-tris(isocyanatohexyl) isocyanuratepresent optionally in admixture with its higher homologues comprisingmore than one isocyanurate ring or (ii) mixtures of the polyisocyanatesrecited under (i) with up to 40 NCO equivalent % based on the entiretyof component a) of other polyisocyanates with aliphatically and/orcycloaliphatically bonded isocyanate groups, and the reaction isperformed with co-use of c) a polyol component consisting essentially ofa polyester polyol having an OH number of 80 to 350 based on (i) acidcomponent consisting to an extent of at least 80 carboxyl equivalent %of adipic acid and/or isophthalic acid and (ii) a polyol componentconsisting at least to an extent of 70 hydroxyl equivalent % of1,6-hexanediol, wherein the amount of component c) makes up 20 to 150 wt% based on the weight of component b) and the reaction is performedwhile maintaining an NCO/OH equivalent ratio of 0.9:1 to 1.1:1, whereinthe alcoholic components b) and c) are reacted with the polyisocyanatecomponent in any desired sequence or in admixture. In one embodiment2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropylacrylate, 2-hydroxypropyl methacrylate or any desired mixtures of thesecompounds are used as component b).

EP 0 347 610 A2 describes UV-curable mixtures containing A) 15-60 wt %based on the total of 100 wt % of A)+B)+C) of reaction products ofhydroxyalkyl acrylates with aliphatic polyisocyanates containing atleast 2 isocyanate groups and at least one uretdione and/ortriisocyanurate and/or biuret group per molecule; B) 30-84 wt % based onthe total of 100 wt % of A)+B)+C) of di- or trifunctional(meth)acrylates having a molecular weight below 500; C) 1-10 wt % basedon the total of 100 wt % of A)+B)+C) of compounds having onepolymerizable group per molecule and a molecular weight below 200, andD) photoinitiators in customary amounts based on the total of 100 wt %of A)+B)+C). In the mixtures component A) may represent reactionproducts of hydroxyethyl acrylate with the uretdione and/ortriisocyanurate and/or biuret based on hexamethylene diisocyanate.

U.S. Pat. No. 4,145,544 discloses a process for producing anethylenically unsaturated isocyanurate comprising the steps of (1)trimerization of an aromatic polyisocyanate to form an NCO-containingisocyanurate, wherein the trimerization is performed in the presence ofan isocyanate trimerization catalyst and a solvent; and (2) reaction ofthe NCO groups present in the NCO-containing isocyanurate with thehydroxyl group of a monohydric alcohol containing a vinylidene group inthe presence of a solvent to form an ethylenically unsaturatedisocyanurate. The solvent employed in steps (1) and (2) is a vinylidenesolvent which is free from groups that react with isocyanate groups andwhich contains at least 20 weight % of an ethylenically unsaturatedpolar solvent. In one embodiment the monohydric alcohol is hydroxypropylmethacrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate,hydroxyethyl acrylate or mixtures thereof.

U.S. Pat. No. 4,159,376 relates to a process for producing anethylenically unsaturated isocyanurate, comprising a first step ofreacting an aromatic polyisocyanate with a monohydric alcohol containinga vinylidene group selected from hydroxypropyl methacrylate,hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxyethyl acrylateor mixtures thereof to form a monoisocyanate-containing urethane, andcomprising a second step of reacting the monoisocyanate-containingurethane with tris(2-hydroxyethyl)isocyanurate to obtain anethylenically unsaturated isocyanurate.

It is an object of the present invention to at least partly overcome atleast one disadvantage of the prior art. It is a further object of theinvention to provide an additive manufacturing process where theproduced objects can exhibit a high resolution coupled with a highstrength. Finally, it is an object of the invention to be able toproduce such objects in a manner which is as cost-efficient and/orindividualized and/or resource-sparing as possible.

The object is achieved in accordance with the invention by a processaccording to Claim 1 and a use according to Claim 12. Advantageousdevelopments are specified in the subsidiary claims. They may becombined as desired unless the opposite is clear from the context.

A process for producing an object from a precursor comprises the stepsof:

-   I) depositing a free-radically crosslinked resin atop a carrier to    obtain a ply of a construction material joined to the carrier which    corresponds to a first selected cross section of the precursor;-   II) depositing a free-radically crosslinked resin atop a previously    applied ply of the construction material to obtain a further ply of    the construction material which corresponds to a further selected    cross section of the precursor and which is joined to the previously    applied ply;-   III) repeating step II) until the precursor is formed;    wherein the depositing of a free-radically crosslinked resin at    least in step II) is effected by exposure and/or irradiation of a    selected region of a free-radically crosslinkable resin    corresponding to the respectively selected cross section of the    precursor, and    wherein the free-radically crosslinkable resin has a viscosity (23°    C., DIN EN ISO 2884-1) of ≥5 mPas to ≤100000 mPas.

In the process the free-radically crosslinkable resin comprises acurable component in which NCO groups and olefinic C═C double bonds arepresent, wherein in the curable component the molar ratio of NCO groupsto olefinic C═C double bonds is in a range from ≥1:5 to ≤5:1.

In the process, after step III) step IV) is further performed:

-   IV) treating the precursor obtained after step III) under conditions    sufficient to at least partially trimerize to isocyanurate groups    NCO groups present in the free-radically crosslinked resin of the    obtained precursor to obtain the object.

In the process according to the invention the object is thus obtained intwo production phases. The first production phase may be regarded as aconstruction phase. This construction phase may be realized by means ofray-optic additive manufacturing processes such as the inkjet method,stereolithography or the DLP (digital light processing) method and isrepresented by steps I), II) und III). The second production phase maybe regarded as a curing phase and is represented by step IV). Here, theprecursor or intermediate object obtained after the construction phaseis converted into a more mechanically durable object, without furtherchanging the shape thereof. In the context of the present invention thematerial from which the precursor is obtained in the additivemanufacturing process is referred to generally as “constructionmaterial”.

Step I) of the process comprises depositing a free-radically crosslinkedresin atop a carrier. This is usually the first step in inkjet,stereolithography and DLP methods. In this way a ply of a constructionmaterial joined to the carrier which corresponds to a first selectedcross section of the precursor is obtained.

As per the instruction of step III), step II) is repeated until thedesired precursor has been formed. Step II) comprises depositing afree-radically crosslinked resin atop a previously applied ply of theconstruction material to obtain a further ply of the constructionmaterial which corresponds to a further selected cross section of theprecursor and which is joined to the previously applied ply. Thepreviously applied ply of the construction material may be the first plyfrom step I) or a ply from a previous run of step II).

It is provided in accordance with the invention that the depositing of afree-radically crosslinked resin at least in step II) (preferably alsoin step I) is effected by exposure and/or irradiation of a selectedregion of a free-radically crosslinkable resin corresponding to therespectively selected cross section of the object. This may be achievedeither by selective exposure (stereolithography, DLP) of the resin or byselective application of the resin followed by an exposure step which,on account of the preceding selective application of the resin, need nolonger be selective (inkjet method).

In the context of the present invention the terms “free-radicallycrosslinkable resin” and “free-radically crosslinked resin” are used.The free-radically crosslinkable resin is converted here into thefree-radically crosslinked resin by the exposure and/or irradiationwhich triggers free-radical crosslinking reactions. “Exposure” is to beunderstood in the present context as meaning the action of light in therange between near-IR and near-UV light (wavelengths of 1400 nm to 315nm). The remaining shorter wavelength ranges are covered by the term“irradiation”, for example far UV light, x-ray radiation, gammaradiation and also electron radiation.

The selecting of the respective cross section is advantageously effectedby means of a CAD program, with which a model of the object to beproduced has been generated. This operation is also known as “slicing”and serves as a basis for controlling the exposure and/or irradiation ofthe free-radically crosslinkable resin.

The free-radically crosslinkable resin has a viscosity (23° C., DIN ENISO 2884-1) of ≥5 mPas to ≤100000 mPas. It may accordingly be regardedas a liquid resin at least for the purposes of additive manufacture. Theviscosity is preferably ≥50 mPas to ≤10000 mPas, more preferably ≥500mPas to ≤1000 mPas.

In the process the free-radically crosslinkable resin further comprisesa curable component in which NCO groups and olefinic C═C double bondsare present, wherein in the curable component the molar ratio of NCOgroups to olefinic C═C double bonds is in a range from ≥1:5 to ≤5:1(preferably ≥1:4 to ≤4:1, more preferably ≥1:3 to ≤3:1). The molecularratio of these functional groups may be determined by integration of thesignals of a sample in the ¹³C-NMR spectrum.

In addition to the curable component the free-radically crosslinkableresin may also comprise a non-curable component in which for examplestabilizers, fillers and the like are encompassed. In the curablecomponent the NCO groups and the olefinic C═C double bonds may bepresent in separate molecules and/or in a common molecule. When NCOgroups and olefinic C═C double bonds are present in separate moleculesthe body obtained after step IV) of the process according to theinvention exhibits an interpenetrating polymer network.

In the process, after step III) step IV) is further performed. This stepcomprises treating the precursor obtained after step III) underconditions sufficient to at least partially trimerize to isocyanurategroups NCO groups present in the free-radically crosslinked resin of theobtained precursor to obtain the object.

The treating in step IV) may in the simplest case be a storage at roomtemperature (20° C.). Storage at a temperature above room temperature isalso possible. During step IV) the NCO groups react with one another toeffect further crosslinking of the previously free-radically crosslinkedmaterial. This reaction results at least partially in trimerization toafford isocyanurate groups. The present invention also comprehends thepossibility that uretdione, allophanate, urea, urethane, biuret,iminooxadiazinedione and/or oxadiazinetrione groups can also be formedfrom the NCO groups. Such side reactions may be specifically employed,for example to influence the glass transition temperature T_(g) of theobtained material.

It is preferable when the reaction is performed until ≤20%, preferably≤10% and more preferably ≤5% of the isocyanate groups present in thecurable component are still present. This may be determined byquantitative IR spectroscopy. It is further preferable when in step IV)≥50%, ≥60%, ≥70% or ≥80% of the isocyanate groups originally present inthe curable component are converted into isocyanurate groups.

It is preferable when step IV) is performed only when the entirety ofthe construction material of the precursor has reached its gel point.The gel point is regarded as reached when in a dynamic mechanicalanalysis (DMA) with a plate/plate oscillation viscometer in accordancewith ISO 6721-10 at 20° C. the graphs of the storage modulus G′ and theloss modulus G″ intersect. The precursor is optionally subjected tofurther exposure and/or radiation to complete free-radical crosslinking.The free-radically crosslinked resin can exhibit a storage modulus G′(DMA, plate/plate oscillation viscometer according to ISO 6721-10 at 20°C. and a shear rate of I/s) of ≥10⁶ Pa.

The free-radically crosslinkable resin may further contain additivessuch as fillers, UV-stabilizers, free-radical inhibitors, antioxidants,mold release agents, water scavengers, slip additives, defoamers, flowagents, theology additives, flame retardants and/or pigments. Theseauxiliaries and additives, excluding fillers and flame retardants, aretypically present in an amount of less than 10 wt %, preferably lessthan 5 wt %, particularly preferably up to 3 wt %, based on thefree-radically crosslinkable resin. Flame retardants are typicallypresent in amounts of not more than 70 wt %, preferably not more than 50wt %, particularly preferably not more than 30 wt %, calculated as thetotal amount of employed flame retardants based on the total weight ofthe free-radically crosslinkable resin.

Suitable fillers are for example AlOH₃, CaCO₃, metal pigments such asTiC₂ and further known customary fillers. These fillers are preferablyemployed in amounts of not more than 70 wt %, preferably not more than50 wt %, particularly preferably not more than 30 wt %, calculated asthe total amount of employed fillers based on the total weight of thefree-radically crosslinkable resin.

Suitable UV stabilizers may preferably be selected from the groupconsisting of piperidine derivatives, for example4-benzoyloxy-2,2,6,6-tetramethylpiperidine,4-benzoyloxy-1,2,2,6,6-pentamethylpiperidine,bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate,bis(1,2,2,6,6-pentamethyl-1-4-piperidinyl) sebacate,bis(2,2,6,6-tetramethyl-4-piperidyl) suberate,bis(2,2,6,6-tetramethyl-4-piperidyl) dodecanedioate; benzophenonederivatives, for example 2,4-dihydroxy-, 2-hydroxy-4-methoxy-,2-hydroxy-4-octoxy-, 2-hydroxy-4-dodecyloxy- or2,2′-dihydroxy-4-dodecyloxybenzophenone; benzotriazole derivatives, forexample 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol,2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol,2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol,2-(5-chloro-2H-benzotriazol-2-yl)-6-(1,1-dimethylethyl)-4-methylphenol,2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol,2-(2H-benzotriazol-2-yl)-6-(l-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol,isooctyl3-(3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxyphenylpropionate),2-(2H-benzotriazol-2-yl)-4,6-bis(1,1-dimethylethyl)phenol,2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol,2-(5-chloro-2H-benzotriazol-2-yl)-4,6-bis(1,1-dimethylethyl)phenol;oxalanilides, for example 2-ethyl-2′-ethoxy- or4-methyl-4′-methoxyoxalanilide; salicylic esters, for example phenylsalicylate, 4-tert-butylphenyl salicylate, 4-tert-octylphenylsalicylate; cinnamic ester derivatives, for example methylα-cyano-β-methyl-4-methoxycinnamate, butylα-cyano-β-methyl-4-methoxycinnamate, ethyl α-cyano-β-phenylcinnamate,isooctyl α-cyano-β-phenylcinnamate; and malonic ester derivatives, suchas dimethyl 4-methoxybenzylidenemalonate, diethyl4-methoxybenzylidenemalonate, dimethyl 4-butoxybenzylidenemalonate.These preferred light stabilizers may be employed either individually orin any desired combinations with one another.

Particularly preferred UV stabilizers are those which completely absorbradiation having a wavelength <400 nm. These include the recitedbenzotriazole derivatives for example. Very particularly preferred UVstabilizers are2-(5-chloro-2H-benzotriazol-2-yl)-6-(1,1-dimethylethyl)-4-methylphenol,2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol and/or2-(5-chloro-2H-benzotriazol-2-yl)-4,6-bis(1,1-dimethylethyl)phenol.

One or more of the UV stabilizers recited by way of example areoptionally added to the free-radically crosslinkable resin preferably inamounts of 0.001 to 3.0 wt %, particularly preferably 0.005 to 2 wt %,calculated as the total amount of employed UV stabilizers based on thetotal weight of the free-radically crosslinkable resin.

Suitable antioxidants are preferably sterically hindered phenols whichmay be selected preferably from the group consisting of2,6-di-tert-butyl-4-methylphenol (ionol), pentaerythritoltetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), octadecyl3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, triethylene glycolbis(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate,2,2′-thiobis(4-methyl-6-tert-butylphenol) and 2,2′-thiodiethylbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. These may be usedeither individually or in any desired combinations with one another asrequired. These antioxidants are preferably employed in amounts of 0.01to 3.0 wt %, particularly preferably 0.02 to 2.0 wt %, calculated as thetotal amount of employed antioxidants based on the total weight of thefree-radically crosslinkable resin.

Suitable free-radical inhibitors/retarders are preferably those whichspecifically inhibit uncontrolled free-radical polymerization of theresin formulation outside the desired (irradiated) region. These arecrucial for good contour sharpness and imaging accuracy in theprecursor. Suitable free-radical inhibitors must be chosen according tothe desired free-radical yield from the irradiation/exposure step andthe polymerization rate and reactivity/selectivity of the double bondcarrier. Suitable free-radical inhibitors are for example2,2-(2,5-thiophendiyl)bis(5-tertbutylbenzoxazole), phenothiazine,hydroquinone, hydroquinone ether, quinone alkydes and nitroxyl compoundsand mixtures thereof, benzoquinones, copper salts, catechols, cresols,nitrobenzene and oxygen. These antioxidants are preferably employed inamounts of 0.001 wt % to 3 wt %.

Embodiments and further aspects of the present invention are elucidatedhereinbelow. They may be combined with one another as desired unless theopposite is clear from the context.

In a preferred embodiment isocyanurate groups are further present in thecurable component; in the curable component the molar ratio of NCOgroups to isocyanurate groups is in a range from ≤100:1 to ≥1:2(preferably ≤70:1 to ≥1:1, more preferably ≤50:1 to ≥2:1) and in thecurable component the molar ratio of olefinic C═C double bonds toisocyanurate groups is in a range from ≤100:1 to ≥1:5 (preferably ≤70:1to ≥1:3, more preferably ≤50:1 bis ≥1:2). The isocyanurate groups arepreferably part of a polyisocyanurate. The molar ratio of NCO groups orC═C double bonds to isocyanurate groups may be determined by integrationof the corresponding signals in the ¹³C-NMR spectrum of the sample.

In a further preferred embodiment the curable component comprises acurable compound which comprises NCO groups and olefinic C═C doublebonds, wherein in the curable compound the molar ratio of NCO groups toolefinic C═C double bonds is in a range from ≥1:5 to ≤5:1 (preferably≥1:4 to ≤4:1, more preferably ≥1:3 to ≤3:1). This compound thus containsthe two recited groups in one molecule.

In a further preferred embodiment the curable component comprises acurable compound which comprises isocyanurate groups, NCO groups andolefinic C═C double bonds, wherein

-   -   in the curable compound the molar ratio of NCO groups to        olefinic C═C double bonds is in a range from ≥1:5 to ≤5:1        (preferably ≥1:4 to ≤4:1, more preferably ≥1:3 to ≤3:1),    -   in the curable compound the molar ratio of NCO groups to        isocyanurate groups is in a range from ≤100:1 to ≥1:2        (preferably ≤70:1 to ≥1:1, more preferably ≤50:1 to ≥2:1) and    -   in the curable compound the molar ratio of olefinic C═C double        bonds to isocyanurate groups is in a range from ≤100:1 to ≥1:5        (preferably ≤70:1 to ≥13, more preferably ≤50:1 to ≥1:2).

This compound thus contains the three recited groups in one molecule.Also included are polymers with the molecular weight distribution ofsaid compound which comprise these groups in each molecule of thepolymer.

To increase the NCO group content in the curable component furtherNCO-functional compounds such as polyisocyanates and NCO-terminatedprepolymers may be added. In this way the mechanical properties of theobtained object may be adapted further.

To increase the double bond content in the curable component furtherdouble-bond-functional compounds having 1 to 6 C═C double bonds may alsobe added. In this way the mechanical properties of the obtained objectand the viscosity of the crosslinkable resin may be adapted further.

In a further preferred embodiment the olefinic double bonds are presentin the curable compound at least partially in the form of (meth)acrylategroups.

In a further preferred embodiment the curable compound is obtainablefrom the reaction of an NCO-terminated polyisocyanate prepolymer with amolar deficiency, based on the free NCO groups, of a hydroxyalkyl(meth)acrylate.

In a further preferred embodiment the curable compound is obtainablefrom the reaction of an NCO-terminated polyisocyanurate with a molardeficiency, based on the free NCO groups, of a hydroxyalkyl(meth)acrylate.

Suitable polyisocyanates for producing the NCO-terminatedpolyisocyanurates are for example those having a molecular weight in therange from 140 to 400 g/mol, having aliphatically, cycloaliphatically,araliphatically and/or aromatically bonded isocyanate groups, forexample 1,4-diisocyanatobutane (BDI), 1,5-diisocyanatopentane (PDI),1,6-diisocyanatohexane (HDI), 2-methyl-1,5-diisocyanatopentane,1,5-diisocyanato-2,2-dimethylpentane, 2,2,4- or2,4,4-trimethyl-1,6-diisocyanatohexane, 1,10-diisocyanatodecane, 1,3-and 1,4-diisocyanatocyclohexane,1,4-diisocyanato-3,3,5-trimethylcyclohexane,1,3-diisocyanato-2-methylcyclohexane,1,3-diisocyanato-4-methylcyclohexane,1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophoronediisocyanate; IPDI),I-isocyanato-1-methyl-4(3)-isocyanatomethylcyclohexane, 2,4′- and4,4′-diisocyanatodicyclohexylmethane (H₁₂MDI), 1,3- and1,4-bis(isocyanatomethyl)cyclohexane, bis(isocyanatomethyl)norbornane(NBDI), 4,4′-diisocyanato-3,3′-dimethyldicyclohexylmethane,4,4′-diisocyanato-3,3′,5,5′-tetramethyldicyclohexylmethane,4,4′-diisocyanato-1,1′-bi(cyclohexyl),4,4′-diisocyanato-3,3′-dimethyl-1,1′-bi(cyclohexyl),4,4′-diisocyanato-2,2′,5,5′-tetramethyl-1,1′-bi(cyclohexyl),1,8-diisocyanato-p-menthane, 1,3-diisocyanatoadamantane,1,3-dimethyl-5,7-diisocyanatoadamantane, 1,3- and1,4-bis(isocyanatomethyl)benzene (xylylene diisocyanate; XDI), 1,3- and1,4-bis(l-isocyanato-1-methylethyl)benzene (TMXDI) andbis(4-(1-isocyanato-1-methylethyl)phenyl) carbonate, 2,4- and2,6-diisocyanatotoluene (TDI), 2,4′- and4,4′-diisocyanatodiphenylmethane (MDI), 1,5-diisocyanatonaphthalene andany desired mixtures of such diisocyanates.

It is further possible in accordance with the invention to also employaliphatic and/or aromatic isocyanate end group-bearing prepolymers, forexample aliphatic or aromatic isocyanate end group-bearing polyether,polyester, polyacrylate, polyepoxide or polycarbonate prepolymers asreactants for the isocyanurate formation. Suitable trimerizationcatalysts are described hereinbelow in connection with anotherembodiment.

Suitable hydroxyalkyl (meth)acrylates are inter alia alkoxyalkyl(meth)acrylates having 2 to 12 carbon atoms in the hydroxyalkyl radical.Preference is given to 2-hydroxyethyl acrylate, the isomer mixtureformed during addition of propylene oxide onto acrylic acid, or4-hydroxybutyl acrylate.

The reaction between the hydroxyalkyl (meth)acrylate and theNCO-terminated polyisocyanurate may be catalyzed by the customaryurethanization catalysts such as DBTL. In this reaction the molar ratioof NCO groups to OH groups of the hydroxyalkyl (meth)acrylate may be ina range from ≥10:1 to ≤1.1:1 (preferably ≥5:1 to ≤1.5:1, more preferably≥4:1 to ≤2:1). The obtained curable compound may have a number-averagemolecular weight M_(n) of ≥200 g/mol to ≤5000 g/mol. This molecularweight is preferably ≥300 g/mol to ≤4000 g/mol, more preferably ≥400g/mol to ≤3000 g/mol.

Particular preference is given to a curable compound obtained from thereaction of an NCO-terminated polyisocyanurate with hydroxyethyl(meth)acrylate, wherein the NCO-terminated polyisocyanurate was obtainedfrom 1,6-hexamethylene diisocyanate in the presence of an isocyanatetrimerization catalyst. This curable compound has a number-averagemolecular weight M_(n) of ≥400 g/mol to ≤3000 g/mol and a molar ratio ofNCO groups and olefinic C═C double bonds in a range from ≥1:5 to ≤5:1,particularly preferably ≥1:3 to ≤3:1, very particularly preferably ≥1:2to ≤2:1.

In a further preferred embodiment the free-radically crosslinkable resinfurther comprises a free-radical starter and/or an isocyanatetrimerization catalyst. To prevent an undesired increase in theviscosity of the free-radically crosslinkable resin, free-radicalstarters and/or isocyanate trimerization catalyst may be added to theresin only immediately before commencement of the process according tothe invention.

Contemplated free-radical starters include thermal and/or photochemicalfree-radical starters (photoinitiators). It is also possible for thermaland photochemical free-radical starters to be employed simultaneously.Suitable thermal free-radical starters are for exampleazobisisobutyronitrile (AIBN), dibenzoylperoxide (DBPO), di-tert-butylperoxide and/or inorganic peroxides such as peroxodisulfates.

Photoinitiators are in principle distinguished into two types, theunimolecular type (I) and the bimolecular type (II). Suitable type (I)systems are aromatic ketone compounds, for example benzophenones incombination with tertiary amines, alkylbenzophenones,4,4′-bis(dimethylamino)benzophenone (Michler's ketone), anthrone andhalogenated benzophenones or mixtures of the recited types. Alsosuitable are type (II) initiators such as benzoin and derivativesthereof, benzil ketals, acylphosphine oxides,2,4,6-trimethylbenzoyldiphenylphosphine oxide, bisacylphosphine oxides,phenylglyoxylic esters, camphorquinone, α-aminoalkylphenones,α,α-dialkoxyacetophenones and α-hydroxyalkylphenones. Specific examplesare Irgacur®500 (a mixture of benzophenone and(1-hydroxycyclohexyl)phenylketone, from Ciba, Lampertheim, DE),Irgacure®819 DW (phenylbis-(2,4,6-trimethylbenzoyl)phosphine oxide, fromCiba, Lampertheim, DE) or Esacure® KIP EM(oligo-[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)-phenyl]-propanones],from Lamberti, Aldizzate, Italy) andbis(4-methoxybenzoyl)diethylgermanium. Mixtures of these compounds mayalso be employed.

It should be ensured that the photoinitiators have a sufficientreactivity toward the radiation source used. A plurality ofphotoinitiators are known on the market. Commercially availablephotoinitiators cover the wavelength range of the entire UV-VISspectrum. Photoinitiators find use in the production of paints, printinginks and adhesives and also in the dental sector.

In the process according to the invention the photoinitiator isgenerally employed in a concentration based on the amount of employedcurable olefinically unsaturated double bond-bearing component of 0.01to 6.0 wt %, preferably of 0.05 to 4.0 wt % and particularly preferablyof 0.1 to 3.0% wt %.

Suitable isocyanate trimerization catalysts are in principle allcompounds which accelerate the addition of isocyanate groups to affordisocyanurate groups and thus crosslink the isocyanate-containingmolecules present.

Suitable isocyanate trimerization catalysts are for example simpletertiary amines, for example triethylamine, tributylamine,N,N-dimethylaniline, N-ethylpiperidine or N,N′-dimethylpiperazine.Suitable catalysts also include the tertiary hydroxyalkylaminesdescribed in GB 2 221 465, for example triethanolamine,N-methyldiethanolamine, dimethylethanolamine, N-isopropyldiethanolamineand 1-(2-hydroxyethyl)pyrrolidine, or the catalyst systems known from GB2 222 161 that consist of mixtures of tertiary bicyclic amines, forexample DBU, with simple low-molecular-weight aliphatic alcohols.

Likewise suitable as isocyanate trimerization catalysts are a pluralityof different metal compounds. Suitable examples are the octoates andnaphthenates of manganese, iron, cobalt, nickel, copper, zinc,zirconium, cerium or lead or mixtures thereof with acetates of lithium,sodium, potassium, calcium or barium that are described as catalysts inDE-A 3 240 613, the sodium and potassium salts of linear or branchedalkanecarboxylic acids having up to 10 carbon atoms that are known fromDE-A 3 219 608, for example of propionic acid, butyric acid, valericacid, caproic acid, heptanoic acid, caprylic acid, pelargonic acid,capric acid and undecylenoic acid, the alkali metal or alkaline earthmetal salts of aliphatic, cycloaliphatic or aromatic mono- andpolycarboxylic acids having 2 to 20 carbon atoms that are known fromEP-A 0 100 129, for example sodium or potassium benzoate, the alkalimetal phenoxides known from GB-A 1 391 066 and GB-A 1 386 399, forexample sodium or potassium phenoxide, the alkali metal and alkalineearth metal oxides, hydroxides, carbonates, alkoxides and phenoxidesknown from GB 809 809, alkali metal salts of enolizable compounds andmetal salts of weak aliphatic or cycloaliphatic carboxylic acids, forexample sodium methoxide, sodium acetate, potassium acetate, sodiumacetoacetate, lead 2-ethylhexanoate and lead naphthenate, the basicalkali metal compounds complexed with crown ethers or polyether alcoholsthat are known from EP-A 0 056 158 and EP-A 0 056 159, for examplecomplexed sodium or potassium carboxylates, the pyrrolidinone-potassiumsalt known from EP-A 0 033 581, the mono- or polynuclear complexcompound of titanium, zirconium and/or hafnium known from application EP13196508.9, for example zirconium tetra-n-butoxide, zirconiumtetra-2-ethylhexanoate and zirconium tetra-2-ethylhexoxide, and tincompounds of the type described in European Polymer Journal, vol. 16,147-148 (1979), for example dibutyltin dichloride, diphenyltindichloride, triphenylstannanol, tributyltin acetate, tributyltin oxide,tin octoate, dibutyl(dimethoxy)stannane and tributyltin imidazolate.

The isocyanate trimerization catalysts may be used in the processaccording to the invention either individually or else in the form ofany desired mixtures with one another.

Isocyanate trimerization catalysts that may be highlighted are sodiumand potassium salts of aliphatic carboxylic acids having 2 to 20 carbonatoms in combination with complexing agents such as crown ethers orpolyethylene glycols or polypropylene glycols and also aliphaticallysubstituted tin compounds or phosphines.

In the process according to the invention the isocyanate trimerizationcatalyst is generally employed in a concentration based on the amount ofthe employed curable component of 0.0005 to 5.0 wt %, preferably of0.0010 to 2.0 wt % and particularly preferably of 0.0015 to 1.0 wt %.

The isocyanate trimerization catalysts finding use in the processaccording to the invention generally have sufficient solubility in thefree-radically crosslinkable resin in the amounts that are required forinitiation of the trimerization reaction. The addition of the isocyanatetrimerization catalyst is therefore preferably effected in the absenceof solvent.

In a further preferred embodiment the free-radical starter is selectedfrom the group: α-hydroxyphenylketone, benzyldimethylketal and/or2,4,6-trimethylbenzoyldiphenylphosphine oxide,bis(4-methoxybenzoyl)diethylgermanium (Ivocerin®)

and/orthe isocyanurate trimerization catalyst is selected from: potassiumacetate, potassium acetate in combination with a crown ether, potassiumacetate in combination with a polyethylene glycol, potassium acetate incombination with a polypropylene glycol, tin octoate, sodium phenoxide,potassium hydroxide, trioctyl phosphine and/or tributyltin oxide.

In a further preferred embodiment the molar ratio of NCO groups toZerewitinoff-active H atoms in the resin is ≥500 (preferably ≥1000, morepreferably ≥2000). The molar ratio of NCO groups to Zerewitinoff-activeH atoms is also known as the NCO index or coefficient. Suitable bearersof Zerewitinoff-active H atoms include in particular compounds havingO—H, N—H or S—H bonds. A proportion of compounds havingZerewitinoff-active H atoms that is as small as possible has the resultthat more NCO groups are available for isocyanurate formation after stepIII).

Alternatively or in addition, this condition may be expressed byspecifying that the resin contains compounds having Zerewitinoff-activeH atoms in an amount of ≤20 weight % (preferably ≤10 weight %, morepreferably ≤5 weight %), based on the mass of the resin.

In a further preferred embodiment the curable component has anumber-average molecular weight M_(n) of ≥200 g/mol to ≤5000 g/mol. Thismolecular weight is preferably ≥300 g/mol to ≤4000 g/mol, morepreferably ≥400 g/mol to ≤3000 g/mol.

In a further preferred embodiment in step IV) the treating of theprecursor obtained after step III) under conditions sufficient to atleast partially trimerize to isocyanurate groups NCO groups present inthe free-radically crosslinked resin of the obtained precursor comprisesa heating of the body to a temperature of ≥60° C. This temperature ispreferably ≥80° C. to ≤250° C., more preferably ≥90° C. to ≤190° C. Thechosen temperature or the chosen temperature range in step IV) may bemaintained for example for ≥5 minutes to ≤48 hours, preferably ≥15minutes to ≤24 hours and more preferably ≥1 hour to ≤12 hours.

In a further preferred embodiment the surface of the precursor obtainedafter step III) and/or of the object obtained after step IV) iscontacted with a compound comprising Zerewitinoff-active H atoms,wherein water occurring as natural atmospheric humidity in theatmosphere surrounding the precursor and/or the object is excluded. In areaction of still free NCO groups with these compounds afunctionalization of the surfaces can be achieved. The compoundcomprising Zerewitinoff-active H atoms may be contacted with the surfaceof the precursor by immersion, spray application or spreading, forexample. A further possibility is contacting via the gas phase, forexample by means of ammonia or water vapor. A catalyst may optionallyaccelerate the reaction.

Examples of compounds suitable as the functionalization reagent arealcohols, amines, acids and derivatives thereof, epoxides and inparticular polyols, for example sugars, polyacrylate polyols, polyesterpolyols, polyether polyols, polyvinyl alcohols, polycarbonate polyols,polyether carbonate polyols and polyester carbonate polyols, long-chainaliphatic alcohols, fluorinated or chlorinated alcohols. Furtherexamples are polyacrylic acid, polyamides, polysiloxanes,polyacrylamides, polyvinylpyrrolidones, polyvinyl butyrate, polyketones,polyether ketones, polyacetals and polyamines. Amines may also be usedfor specific formation of ureas.

It is preferable to employ a long-chain alkyl alcohol, a long-chain(secondary) alkyl amine, a fatty acid, an epoxidized fatty acid ester, a(per)fluorinated long-chain alcohol or mixtures thereof. “Long-chain” isto be understood here as meaning from 6 carbon atoms, preferably from 8carbon atoms, more preferably from 10 carbon atoms in the longest chainof the compound. The production of modified polyisocyanates is known inprinciple and described in EP-A 0 206 059 and EP-A 0 540 985 forexample. It is effected preferably at temperatures of 40° C. to 180° C.

In a further preferred embodiment the process has the followingadditional features:

-   -   the carrier is arranged inside a container and is vertically        lowerable in the direction of the gravitational force,    -   the container contains the free-radically crosslinkable resin in        an amount sufficient to cover at least the carrier and        crosslinked resin deposited atop the carrier,    -   before each step II) the carrier is lowered by a predetermined        distance so that above the uppermost ply of the construction        material viewed in the vertical direction a layer of the        free-radically crosslinkable resin is formed and    -   in step II) an energy beam exposes and/or irradiates the        selected region of the layer of the free-radically crosslinkable        resin corresponding to the respectively selected cross section        of the precursor.

Accordingly, this embodiment covers the additive manufacturing processof stereolithography (SLA). The carrier may for example be lowered by apredetermined distance of ≥1 μm to ≤2000 μm in each case.

In a further preferred embodiment the process has the followingadditional features:

-   -   the carrier is arranged inside a container and is vertically        raisable counter to the direction of the gravitational force,    -   the container provides the free-radically crosslinkable resin,    -   before each step II) the carrier is raised by a predetermined        distance so that below the lowermost ply of the construction        material viewed in the vertical direction a layer of the        free-radically crosslinkable resin is formed and    -   in step II) a plurality of energy beams simultaneously expose        and/or irradiate the selected region of the layer of the        free-radically crosslinkable resin corresponding to the        respectively selected cross section of the precursor.

Accordingly, this embodiment covers the additive manufacturing processof DLP technology when the plurality of energy beams generate the imageto be provided by exposure and/or irradiation via an array ofindividually controllable micromirrors. The carrier may for example beraised by a predetermined distance of ≥1 μm to ≤2000 μm in each case.

In a further preferred embodiment the process has the followingadditional features:

-   -   in step II) the free-radically crosslinkable resin is applied        from a printing head corresponding to the respectively selected        cross section of the precursor and is subsequently exposed        and/or irradiated.

Accordingly, this embodiment covers the additive manufacturing processof the inkjet method: the crosslinkable resin, optionally separatelyfrom the catalysts according to the invention, is applied selectivelyvia one or more printing heads and the subsequent curing by irradiationand/or exposure may be nonselective, for example via a UV lamp. The oneor more printing heads for application of the resin may be (modified)printing heads for inkjet printing processes. The carrier may beconfigured to be movable away from the printing head or the printinghead may be configured to be movable away from the carrier. Theincrements of the spacing movements between the carrier and the printinghead may be in a range from ≥1 μm to ≤2000 μm for example.

In this embodiment in particular through a small number of repetitionsof step II) a very thin precursor may be constructed. This precursor mayalso be constructed on a substrate as the carrier which fulfills afunction in the later use of the produced object. It is then justifiedto refer to application of a surface atop the carrier or the substrate.The substrate may be an interior or exterior part of a vehicle forexample. The process according to the invention according to thisembodiment may then also be regarded as a painting process.

The invention likewise relates to the use of a free-radicallycrosslinkable resin having a viscosity (23° C., DIN EN ISO 2884-1) of ≥5mPas to ≤100000 mPas in an additive manufacturing process, wherein theresin comprises a curable compound having isocyanurate groups, NCOgroups and olefinic C═C double bonds,

-   -   wherein the molar ratio of NCO groups to olefinic C═C double        bonds is in a range from ≥1:5 to ≤5:1 (preferably ≥1:4 to ≤4:1,        more preferably ≥1:3 to ≤3:1),    -   the molar ratio of NCO groups to isocyanurate groups is in a        range from ≤100:1 to ≥1:2 (preferably ≤70:1 to ≥1:1, more        preferably ≤50:1 to ≥2:1) and    -   the molar ratio of olefinic C═C double bonds to isocyanurate        groups is in a range from ≤100:1 to ≥1:5 (preferably ≤70:1 to        ≥1:3, more preferably ≤50:1 to ≥1:2).

In a preferred embodiment of the use the resin further comprises afree-radical starter and/or an isocyanate trimerization catalyst. It ispreferable when the free-radical starter is selected from the group:α-hydroxyphenylketone, benzyldimethylketal und/or2,4,6-trimethylbenzoyldipbenylphosphine oxide,bis(4-methoxybenzoyl)diethylgermanium,

and/orthe isocyanurate trimerization catalyst is selected from: potassiumacetate, potassium acetate in combination with a crown ether, potassiumacetate in combination with a polyethylene glycol, potassium acetate incombination with a polypropylene glycol, tin octoate, sodium phenoxide,potassium hydroxide, trioctyl phosphine and/or tributyltin oxide.

In terms of the curable compound the same considerations and preferredembodiments apply for the use according to the invention as previouslywith regard to the process according to the invention. To avoidunnecessary repetition they are not recited again. It is merely notedthat in a further preferred embodiment the olefinic double bonds arepresent at least partially in the form of (meth)acrylate groups in thecurable compound and that in a further preferred embodiment the curablecompound is obtainable from the reaction of an NCO-terminatedpolyisocyanurate with a molar deficiency, based on the free NCO groups,of a hydroxyalkyl (meth)acrylate.

In a further preferred embodiment of the use the additive manufacturingprocess comprises the exposure and/or irradiation of a previouslyselected region of the free-radically crosslinkable resin. The additivemanufacturing process may be a stereolithography process or a DLP(digital light processing) process, for example. “Exposure” is to beunderstood in the present context as meaning the action of light in therange between near-IR and near-UV light (wavelengths of 1400 nm to 315nm). The remaining shorter wavelength ranges are covered by the term“irradiation”, for example far UV light, x-ray radiation, gammaradiation and also electron radiation.

The invention further provides a polymer obtainable by the crosslinkingof a resin having a viscosity (23° C., DIN EN ISO 2884-1) of ≥5 mPas to≤100000 mPas, wherein the resin comprises a curable component whichcomprises NCO groups and olefinic C═C double bonds, wherein the molarratio of NCO groups to olefinic C═C double bonds is in a range from ≥1:5to ≤5:1 (preferably ≥1:4 to ≤4:1, more preferably ≥1:3 to ≤3:1).

It is preferable when the polymer is a polymer obtainable by thecrosslinking of a resin having a viscosity (23° C., DIN EN ISO 2884-1)of ≥5 mPas to ≤100000 mPas, wherein the resin comprises a curablecomponent which comprises isocyanurate, NCO groups and olefinic C═Cdouble bonds,

-   -   wherein the molar ratio of NCO groups to olefinic C═C double        bonds is in a range from ≥1:5 to ≤5:1 (preferably ≥1:4 to ≤4:1,        more preferably ≥1:3 to ≤3:1).    -   the molar ratio of NCO groups to isocyanurate groups is in a        range from ≤100:1 to ≥1:2 (preferably ≤70:1 to ≥1:1, more        preferably ≤50:1 to ≥2:1) and    -   the molar ratio of olefinic C═C double bonds to isocyanurate        groups is in a range from ≤100:1 to ≥1:5 (preferably ≤70:1 to        ≥1:3, more preferably ≤50:1 to ≥1:2).

The crosslinking may in particular be effected via a two-stage processcomposed of free-radical crosslinking of the C═C double bonds followedby trimerization (including trimerization side reactions) of the NCOgroups to afford isocyanurate groups.

In terms of the curable compound the same considerations and preferredembodiments apply for the use according to the invention as previouslywith regard to the process according to the invention. To avoidunnecessary repetition they are not recited again. It is merely notedthat in a preferred embodiment the olefinic double bonds are present atleast partially in the form of (meth)acrylate groups in the curablecompound and that in a further preferred embodiment the curable compoundis obtainable from the reaction of an NCO-terminated polyisocyanuratewith a molar deficiency, based on the free NCO groups, of a hydroxyalkyl(meth)acrylate.

EXAMPLES

The invention is more particularly elucidated with reference to theexamples which follow but without any intention to limit the inventionthereto.

The formulations of free-radically crosslinkable resins reported in thetables 1 and 2 were produced. The data in the table relate to parts byweight unless otherwise stated. Entries designated with a V arecomparative examples.

TABLE 1 1 2 Isocyanate 1 56 70 Isocyanate 2 14 — Acrylate 1 30 30Photoinitiator 1 0.8 wt % of the acrylate 0.8 wt % of the acrylateInhibitor 0.08 wt % of the acrylate 0.08 wt % of the acrylate KOAccatalyst 1.5 wt % of isocyanates 1 1.5 wt % of isocyanate 1 and 2

TABLE 2 Formulation 3 4 5 6 7 8 9 V2 V3 10 Components g g g g g g g g gg Isocyanate 1 30 15 21 10.5 15 21 15 11 Isocyanate 3 15 10.5 21Isocyanate 4 6 Isocyanate 5 10 Acrylate 1 9 9 9 6 9 21 9 Acrylate 2 9 99 Photoinitiator 2 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 Catalyst 0.90.9 0.9 0.9 0.9 0.9 0.9 0.9 0.9 0.9Isocyanate I: reaction product of the 1,6-HDI trimer with hydroxyethylacrylate and the following idealized structure:

Isocyanate 2: NCO-terminated, polyether-modified HDI prepolymer(Desmodur® N3100 Covestro Deutschland AG)Isocyanate 3: aliphatic polyisocyanate, low viscosity HDI trimerisate(Desmodur® N3600 Covestro Deutschland AG)Isocyanate 4: Isophorone diisocyanate (Desmodur® Covestro DeutschlandAG)Isocyanate 5: aliphatic, mostly linear isocyanate-functional prepolymersof a polyether based on hexamethylene diisocyanate (Desmodur® XP 2617Covestro Deutschland AG)Acrylate 1: 1,6-hexanediol diacrylate (analytical quality obtained fromSigma-Aldrich)Acrylate 2: isobornyl acrylate (analytical quality obtained fromSigma-Aldrich)Photoinitiator 1: diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide; TPO(obtained from Sigma-Aldrich)Photoinitiator 2: 2-hydroxy-2-methylpropiophenone; Darocur 1173(obtained from Sigma-Aldrich)Inhibitor: BBOT:2,2′-(2,5-thiophenediyl)bis(5-(1,1-dimethylethyl))benzoxazole; UVblocker (obtained from Sigma-Aldrich)Catalyst: potassium acetate+18-crown-6 crown ether in diethylene glycol(components obtained from Sigma-Aldrich and mixed in the ratio: 0.148 gof potassium acetate+0.485 g of 18-crown-6 ether+3.115 g of diethyleneglycol.

The resin formulation Autodesk Standard Clear Prototyping Resin PR48 waschosen for the comparative example V1. This resin formulation containsabout 40 weight % of the aliphatic urethane acrylate Ebecryl® 8210,about 40 weight % of the ethoxylated pentaerythritol tetraacrylateSartomer® SR 494, TPO as a photoinitiator, about 20 weight % of themonofunctional urethane acrylate Rahn Genomer® 1122 as a reactivediluent and Mayzo® OB+(2,2′-(2,5-thiophenediyl)bis(5-tert-butylbenzoxazole)) as a UV blocker.

All listed formulations were, unless described otherwise, mixed byadding all components in the order given by the recipe in a Thinky ARE250 Speedmixer for 2 minutes at 2000 rpm.

Formulations 1 and 2 according to the invention and the formulation ofthe comparative example V1 were used to produce standard S3 test barsfor tensile tests on an Autodesk Ember DLP-based 3D printing apparatus.The wavelength for the exposure was 405 nm. The individual layers of thetest bars were arranged parallel to the tensile direction. The layerthickness was 50 μm in each case. The exposure time was 5 s/layer.

The precursors produced from formulations 1 and 2 were subsequentlyheated for 30 minutes at 130° C. in a forced-air drying cabinet.

The thus obtained test bars had the properties reported in the table 3below.

TABLE 3 V1 1 2 Modulus of elasticity [GPa], DIN 53504 1 1.3 1.2 Tensilestrength [MPa], DIN 53504 34 48 48 Elongation at break [%], DIN 535045.4 4.4 5.1 Glass transition temperature [° C.], DSC, 20 K/min 15 70 70

Examples 1 and 2 according to the invention, when compared tocomparative example V1, show a significantly higher tensile strength atcomparable elongation at break.

The formulations 3 to 10 according to the invention and the comparativeformulations V2 and V3 were coated onto a glass plate using a doctorknife as 400 micrometer thick layers and pre-cured using UV lamps(gallium-doped mercury lamp and undoped mercury lamp) at a line speed of5.0 m/min and a radiation dose of 1400 mJ/cm². After that the precursorsobtained from the formulations 3 to 10 according to the invention andthe comparative formulations V2 and V3 were heated at 180° C. for 10minutes in a forced-air drying cabinet.

Using a Fischerscope HC100C apparatus from Fischer Technology Inc., USAthe microhardness and according to DIN EN ISO 14577-1b using theforce-indentation curve the Martens hardness were determined for thecoatings thus obtained and listed in table 4.

Furthermore, the optical appearance of the coatings thus obtained wasdescribed and also listed in table 4.

After curing at the given UV dose all samples are self-supporting, i.e.there is no flow of the samples from the glass plate visible even aftervertical positioning of the plates. This self-supporting is an indicatorfor a rapid sufficient modulus generation which enables the productionof an article according to the invention.

TABLE 4 3 4 5 6 7 8 9 V2 V3 10 Martens 126 128 126 154 140 161 157brittle brittle 101 hardness not not [N/mm²] determinable determinableoptical clear clear clear clear clear clear clear cloudy clear clearappearance

The results of table 4 clearly show that particularly good results andcompatible, transparently cured products are achieved with thecomponents according to the invention, whereas the comparative examplesare brittle and frequently cloudy. In contrast to the comparativeexamples the mixtures according to the invention contain isocyanategroups and double bond carriers in at least one formulation component(in this case, isocyanate 1). Surprisingly this leads to a stabilizationof the otherwise incompatible (as shown in V2 and V3) networks whichform from polyisocyanurate and poly(meth)acrylate groups.

1. Process for producing an object from a precursor, comprising thesteps of: I) depositing a free-radically crosslinked resin atop acarrier to obtain a ply of a construction material joined to the carrierwhich corresponds to a first selected cross section of the precursor;II) depositing a free-radically crosslinked resin atop a previouslyapplied ply of the construction material to obtain a further ply of theconstruction material which corresponds to a further selected crosssection of the precursor and which is joined to the previously appliedply; III) repeating step II) until the precursor is formed; wherein thedepositing of a free-radically crosslinked resin at least in step II) iseffected by exposure and/or irradiation of a selected region of afree-radically crosslinkable resin corresponding to the respectivelyselected cross section of the precursor and wherein the free-radicallycrosslinkable resin has a viscosity (23° C., DIN EN ISO 2884-1) of ≥5mPas to ≤100000 mPas, characterized in that the free-radicallycrosslinkable resin has a curable component in which NCO groups andolefinic C═C double bonds are present, wherein in the curable compoundthe molar ratio of NCO groups to olefinic C═C double bonds is in a rangefrom ≥1:5 to ≤5:1, and in that, after step III), step IV) is furtherperformed: IV) treating the precursor obtained after step III) underconditions sufficient to at least partially trimerize to isocyanurategroups NCO groups present in the free-radically crosslinked resin of theobtained precursor to obtain the object.
 2. Process according to claim1, characterized in that isocyanurate groups are further present in thecurable component, wherein the molar ratio of NCO groups to isocyanurategroups is in a range from ≤100:1 to ≥1:2 and in the curable componentthe molar ratio of olefinic C═C double bonds to isocyanurate groups isin a range from ≤100:1 to ≥1:5.
 3. Process according to claim 1,characterized in that the curable component comprises a curable compoundwhich comprises NCO groups and olefinic C═C double bonds, wherein in thecurable compound the molar ratio of NCO groups to olefinic C═C doublebonds is in a range from ≥1:5 to ≤5:1.
 4. Process according to claim 3,characterized in that the curable component comprises a curable compoundcomprising isocyanurate groups, NCO groups and olefinic C═C doublebonds, wherein in the curable compound the molar ratio of NCO groups toolefinic C═C double bonds is in a range from ≥1:5 to ≤5:1, in thecurable compound the molar ratio of NCO groups to isocyanurate groups isin a range from ≤100:1 to ≥1:2, and in the curable compound the molarratio of olefinic C═C double bonds to isocyanurate groups is in a rangefrom ≤100:1 to ≥1:5.
 5. Process according to claim 1, characterized inthat the free-radically crosslinkable resin further comprises afree-radical starter and/or an isocyanate trimerization catalyst. 6.Process according to claim 5, characterized in that at least onefree-radical starter is selected from the group: α-hydroxyphenylketone,benzyldimethylketal, 2,4,6-trimethylbenzoyldiphenylphosphine oxide,bis(4-methoxybenzoyl)diethylgermanium and any combination of at leasttwo thereof and/or the isocyanurate trimerization catalyst is selectedfrom: potassium acetate, potassium acetate in combination with a crownether, potassium acetate in combination with a polyethylene glycol,potassium acetate in combination with a polypropylene glycol, tinoctoate, sodium phenoxide, potassium hydroxide, trioctyl phosphineand/or tributyltin oxide.
 7. Process according to claim 1, characterizedin that in the resin the molar ratio of NCO groups toZerewitinoff-active H atoms is ≥500.
 8. Process according to claim 1,characterized in that the curable component has a number-averagemolecular weight M_(n) of ≥200 g/mol to ≤5000 g/mol.
 9. Processaccording to claim 1, characterized in that in step IV) the treating ofthe precursor obtained after step III) under conditions sufficient to atleast partially trimerize to isocyanurate groups NCO groups present inthe free-radically crosslinked resin of the obtained precursor comprisesa heating of the body to a temperature of ≥60° C.
 10. Process accordingto claim 1, characterized in that the surface of the precursor obtainedafter step III) and/or of the object obtained after step IV) iscontacted with a compound comprising Zerewitinoff-active H atoms,wherein water occurring as natural atmospheric humidity in theatmosphere surrounding the precursor and/or the object is excluded. 11.Process according to claim 1, characterized in that: the carrier isarranged inside a container and is vertically lowerable in the directionof the gravitational force, the container contains the free-radicallycrosslinkable resin in an amount sufficient to cover at least thecarrier and crosslinked resin deposited atop the carrier, before eachstep II) the carrier is lowered by a predetermined distance so thatabove the uppermost ply of the construction material viewed in thevertical direction a layer of the free-radically crosslinkable resin isformed and in step II) an energy beam exposes and/or irradiates theselected region of the layer of the free-radically crosslinkable resincorresponding to the respectively selected cross section of theprecursor.
 12. Process according to claim 1, characterized in that: thecarrier is arranged inside a container and is vertically raisablecounter to the direction of the gravitational force, the containerprovides the free-radically crosslinkable resin, before each step II)the carrier is raised by a predetermined distance so that below thelowermost ply of the construction material viewed in the verticaldirection a layer of the free-radically crosslinkable resin is formedand in step II) a plurality of energy beams simultaneously expose and/orirradiate the selected region of the layer of the free-radicallycrosslinkable resin corresponding to the respectively selected crosssection of the precursor.
 13. Process according to claim 1,characterized in that: in step II) the free-radically crosslinkableresin is applied from one or more printing heads corresponding to therespectively selected cross section of the precursor and is subsequentlyexposed and/or irradiated.
 14. Use of a free-radically crosslinkableresin having a viscosity (23° C., DIN EN ISO 2884-1) of ≥5 mPas to≤100000 mPas in an additive manufacturing process, characterized in thatthe resin has a curable compound which comprises isocyanurate groups,NCO groups and olefinic C═C double bonds, wherein the molar ratio of NCOgroups to olefinic C═C double bonds is in a range from ≥1:5 to ≤5:1, inthe curable compound the molar ratio of NCO groups to isocyanurategroups is in a range from ≤100:1 to ≥1:2, and in the curable compoundthe molar ratio of olefinic C═C double bonds to isocyanurate groups isin a range from ≤100:1 to ≥1:5.
 15. Polymer obtainable by crosslinkingof a resin having a viscosity (23° C., DIN EN ISO 2884-1) of ≥5 mPas to≤100000 mPas, characterized in that the resin comprises a curablecomponent comprising NCO groups and olefinic C═C double bonds, whereinthe molar ratio of NCO groups to olefinic C═C double bonds is in a rangefrom ≥1:5 to ≤5:1.